Text I.

Л.Н.ВОЛКОВА

Методические указания

По обучению чтению технической литературы

На английском языке по специальности

«Материаловедение в машиностроении»

(часть II)

Издательство МВТУ

HEAT TREATMENT FOR STEELS

Text I.

Ex. 1. Догадайтесь о значении следующих слов и словосочетаний и переведите их.

stage of manufacture; heat-treated components; combination of properties; thermal treatment - coefficient of thermal expan­sion; finished product; to machine components - machining - che­mical machining; to reflect - reflectivity; interior of a compo­nent; composition of the alloy; effects of cold work; well-known industrial practices; carburizing; nitriding.

INTRODUCTION

The application of heat treatment to metal to make its wor­king easier or to harden it is an ancient art. Today, nearly all components are subjected to some form of heat treatment at some stage of their manufacture, while some components undergo numerous and often complicated thermal treatments to develop the optimum combination of properties in the finished product. The first use of heat treatment was merely to change the hardness and ductility of alloys, and this is still the most usual objec­tive, though modern herb-treated alloys have been developed to obtain a variety of mechanical properties.

Metals and alloys are heat treated for a number of purposes, but primarily to (1) increase their hardness and strength, (2) improve ductility, or (3) soften them for subsequent metal forming or cutting operations. Various heat treatments may also be used to relieve stresses due to machining, forging, or casting, eli­minate hydrogen picked up during chemical machining or electro­plating, eliminate the effects of cold-work, and give a more unite form grain size. Some alloys for special applications are heat-treated to modify physical properties. Thus, electrical and magnetic properties, reflectivity, density, and coefficient of thermal expansion all can be changed to some extent¹ by heat treatment. In addition, it is often desirable to develop at the surface of a component a combination of properties which are quite different from those in its interior. This may be done subjecting the surface and the interior to different heat treat­ments or by changing the composition of the alloy near the surface, either before or at the same time as the component is heat-treated. Processes of the latter kind are numerous and include such well-known industrial practices as carburizing the nitriding.

Note to the text:

1. to some extent - до некоторой степени

Ex. 2.

1. For what main purposes are metals and alloys heat treated?

2. What physical properties can be changed by heat treatment?
3. What combination of properties can be developed by carburi­zing or nitriding?

4. How is it possible to develop different properties at the surface and in the interior?

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